Shield Feeder or Plug Feeder

ABSTRACT

The invention relates to a feeder insert for inserting into a casting mold used for casting metals, comprising a feeder body  1 , which extends along a longitudinal axis  13  of the feeder and has a feeder cavity  2 , comprising a bottom side that can be inserted into the casting mold and a top side  7  that is situated opposite the bottom side. According to the invention, an energy absorbing device ( 8, 9 ) is provided on the top side  7  of the feeder body  1.

The invention relates to a feeder insert for inserting into a castingmold used for casting metals, comprising a feeder body, which extendsalong a main axis of the feeder and has a feeder cavity, comprising abottom side that can be inserted into the casting mold and a top sidethat is situated opposite the bottom side.

In the production of molded parts in a foundry, liquid metal isintroduced into a casting mold. During the solidifying process, thevolume of the material introduced decreases. Therefore, so-calledfeeders, i.e. open or closed spaces, are regularly inserted in or on thecasting mold in order to compensate for the volume deficit during thesolidification of the casting and to prevent the formation of voids inthe casting. For this purpose, the feeders are connected to the castingor to the region of the casting that is at risk and are usually arrangedabove or to the side of the mold cavity.

In the production of the casting mold, firstly a pattern plate whichcorresponds to the inner contour of the mold cavity is produced. At thelocations at which a feeder insert is to be fitted, a holding device isusually provided, for example a pin for fixing the position of thefeeder insert. Once the feeders are fitted on the pattern plate, amolding material, generally molding sand, is applied to the patternplate in such a way that the feeder insert is encapsulated. In a furtherstep, the molding material is then compacted, so that the feeder isenclosed by the compacted molding material. During the compaction of themolding material, relatively high compaction pressures are used. Thereis therefore the risk that the feeder insert will not withstand thecompressive forces occurring during the compaction and will break up. Asa result, it is no longer possible for controlled feeding of the castingto take place during the casting process. It has been attempted tocounter this problem by using particularly stable and thick-walledfeeder inserts. However, this is quite expensive because of theincreased material requirement.

Another approach is to absorb the compressive forces occurring duringthe compression molding by means of so-called expansion mandrels.Expansion mandrels generally comprise a tubular element for fastening onthe pattern plate, a spring arranged in the tubular element and amandrel tip element, which rests on the spring and can be displacedtelescopically in the longitudinal direction. After the expansionmandrel is fastened on the pattern plate, a feeder insert is placed onit, the bottom surface of which is at a certain distance from thesurface of the pattern in the initial arrangement, i.e. before themolding material is introduced. During the subsequent introduction andcompaction of the molding material, the feeder insert is moved in thedirection of the surface of the pattern against the spring force exertedby the expansion mandrel, without the bottom side of the feeder insertcoming into direct contact with the surface of the pattern.

Therefore, destruction of the feeder insert is prevented even when highcompaction forces are used.

A sprung mandrel for holding feeders and comprising a holding andguiding part, a spring and an axially movable cover is described in DE41 19 192 A1. The cover is formed like a cup and extends over the springand the holding and guiding part.

An arrangement comprising a cup-shaped feeder and a mandrel is describedin DE 195 03 456 C1. The mandrel is fastened on a casting pattern. Thefeeder is mounted on the mandrel in such a way that a distance ismaintained between its lower end and the surface of the casting pattern.A first and a second rigidly preset stop are preset on the mandrel for afirst and a second distance-maintaining position. The feeder assumes thesecond distance-maintaining position, near the surface of the castingpattern, during the compaction of the molding sand, by a predeterminedbreaking point in the bottom of the feeder being made to open by thecounter pressure emanating from the mandrel, allowing the feeder to goover into the second distance-maintaining position.

Before the feeder inserts are inserted, the expansion mandrels mustfirst be fastened on the pattern plate, which is a laborious procedure.Furthermore, with an expansion mandrel, a precisely arranged knock-offedge can only be realized with difficulty. This knock-off edge isprovided to make it possible for the residual feeder, i.e. the metalremaining in the feeder insert after casting, to be separated from thecasting. The cleaning effort is therefore generally quite high.Expansion mandrels are also quite expensive and susceptible to wear.

The invention was therefore based on the object of providing a feederinsert which can withstand the forces occurring during the compaction ofthe molding material. Furthermore, at least in a preferred embodiment ofthe feeder insert, it should be possible to provide a knock-off edgewhich makes it possible for the residual feeder to be preciselyseparated from the casting.

This object is achieved by a feeder insert with the features of patentclaim 1. Advantageous embodiments are the subject of the dependentclaims.

The feeder insert according to the invention comprises a feeder body, inwhich a feeder cavity is arranged. The feeder body may in fact be of anydesired form and is formed in the customary way. The feeder body usuallyhas an approximately tubular form. The feeder thereby has a height whichis greater than its diameter. The feeder body may for example becylindrically formed. However, it is also possible that the feeder bodytapers for example toward the bottom side, so that a small standingsurface of the feeder insert on the pattern plate is achieved. Thefeeder body has on its bottom side an opening through which the feedercavity is in connection with the cavity of the casting mold. The feederbody may likewise be open on its top side. However, it may equally beclosed on its top side. The feeder body consists of the materials thatare customary for the production of feeders and may be formed in aninsulating and/or exothermic manner. Appropriate materials are known toa person skilled in the art. According to the invention, an energyabsorbing device is provided on the top side of the feeder body. Thefeeder insert is fitted directly on the surface of the pattern plate, sothat in a preferred embodiment a breaking edge can be created at thelower termination of the feeder insert. An energy absorbing device,which absorbs the forces or energy acting on the feeder insert duringthe compaction of the molding material, is provided on the top side ofthe feeder insert. This avoids the feeder body being compressed by theforces acting during the compaction and thereby broken up. The feedertherefore does not require an expansion mandrel to absorb the forcesacting during the compaction of the molding material. However, it may beadvisable to provide a fixed mandrel for positioning and fixing thefeeder insert according to the invention.

The energy absorbing device preferably covers at least the top side ofthe feeder body. In this way, forces which act in the direction of thepattern plate parallel to the longitudinal axis of the feeder body canbe substantially absorbed or at least significantly reduced. Since theenergy absorbing device covers the entire top side of the feeder body,shearing off of parts of the feeder body during the compaction of themolding material can also be prevented.

The energy absorbing device may be formed in various ways. For instance,according to a first embodiment, the energy absorbing device maycomprise a deformation element. The irreversible deforming of thedeformation element has the effect that the force which acts on the topside of the feeder body during the compaction of the molding material isabsorbed and the energy introduced is destroyed, so that no damage tothe feeder body can occur. The deformation element may be formed invarious ways. In a very simple embodiment, the deformation element mayfor example be a plate which is produced from a suitable deformablematerial, for example a rigid foam. Such a rigid foam may be a polymerfoam, such as for example a polystyrene foam, or else a foam of aninorganic material, for example a foamed glass. The deformation elementmay also consist of metal and have a form which makes it possible toabsorb energy by deforming of the deformation element. For example, thedeformation element may be formed in a way similar to a can, the sidewalls being folded like an accordion. The can is compressed during thepressing of the molding material, by the accordion structure beingfurther pressed together. Other structures are also possible. Forexample, it is conceivable that the deformation element has a honeycombstructure which is compressed under the action of the forces actingduring the compression molding.

According to another embodiment, the energy absorbing device is formedas an elastic element. For this purpose, the energy absorbing device mayfor example comprise a spring element which is compressed during thepressing of the molding material, in order in this way to absorb theforces acting on the feeder body. However, other elastic elements mayalso be used. For example, it is also possible to use a rubber ring or arubber plate which absorbs energy introduced into the feeder body byelastic deformation.

The energy absorbing device may also comprise a friction element. Theenergy introduced into the energy absorbing device during thecompression molding is then converted into heat by the friction betweentwo appropriately formed surfaces and is destroyed.

The energy absorbing device may be formed in various ways. In apreferred embodiment, it comprises a plate-shaped element which isarranged substantially perpendicular to the longitudinal axis of thefeeder and has an extent which corresponds at least to the cross sectionof the top side of the feeder body. In the simplest embodiment, theenergy absorbing device is for example a plate, for example a platewhich can be deformed in the direction of the longitudinal axis of thefeeder and is placed on the top side of the feeder body. Theplate-shaped element may, however, also be formed in such a way that ithas the form of a cap. In this embodiment, the plate-shaped elementcomprises a skirt running along its periphery that preferably reachesover the edge running around the circumference of the top side of thefeeder body, in the direction of the side face of the feeder body, inthe case where the plate-shaped element is resting on the top side ofthe feeder body. This facilitates the fixing of the energy absorbingdevice on the top side of the feeder body. The top side and bottom sideof the plate-shaped element may be formed as substantially parallelrunning surfaces. However, the plate-shaped element may also have forexample a greater thickness in the middle of its surface than at theperiphery, so that the energy absorbing device is given a roof-shapedform.

In a preferred embodiment, the plate-shaped element has at least onecontinuation and the feeder body has on the top side at least onereceptacle in which the continuation is received. The continuation maybe formed, for example, as a peripheral ring on the bottom side of theplate-shaped element, which is inserted in a groove formed on the topside of the feeder body in the form of a peripheral circle. This allowsthe plate-shaped element to be fixed for example in a position such thatit is not displaced during the introduction of the molding material andthe subsequent compaction.

However, the continuation is formed with preference as a rod-shaped plugelement and the receptacle is formed with preference as a sleeve. Withpreference, at least two rod-shaped plug elements, but with particularpreference three or four or more plug elements, are provided on the sideof the plate-shaped element that is facing the feeder body. The lengthof the plug elements may be chosen to be very short if the plugs merelyserve for fixing the position of the energy absorbing device. However,the rod-shaped plug elements are used with preference in cooperationwith the sleeves introduced into the feeder body for absorbing anddestroying the energy which is introduced into the feeder body duringthe compression molding. The sleeves may be produced as a separatecomponent which is produced for example from plastic or metal andintroduced into the feeder body. However, it is also possible to formthe feeder body directly in such a way that corresponding depressions onthe top side are formed directly in the material of the feeder body.

As already explained, the rod-shaped plug elements may be used incooperation with the sleeves for absorbing and destroying energy whichwould otherwise bring about a compression of the feeder body, which maylead to the breaking up of the feeder body.

In a first embodiment, arranged for this purpose along the wall of thesleeve are projections by which the diameter of the sleeve is reduced tothe extent that it becomes slightly smaller than the diameter of therod-shaped plug element. The projections may be formed for example asridges which run in the direction of the longitudinal axis of the feederbody along the wall of the sleeve. If the rod-shaped plug elements ofthe plate-shaped element are inserted into the sleeve, the plate-shapedelement is initially kept at a specific distance from the top side ofthe feeder body. If molding material is then introduced around thefeeder insert and subsequently compacted, the plate-shaped element ismoved in the direction of the longitudinal axis of the feeder bodytoward the top side of the feeder body. The rod-shaped plug elementsthereby deform the projections arranged along the wall of the sleeve, sothat energy which would otherwise lead to compression of the feeder bodyis absorbed on the one hand by the deformation and on the other hand bythe friction between the sleeve and the rod-shaped plug element.

According to another embodiment, a spring element which produces acounterforce when the rod-shaped plug element penetrates the sleeve mayalso be provided in the sleeve. Energy which could otherwise bring abouta compression of the feeder body is once again absorbed by the pressingtogether of the spring element. The spring element may also be formed insuch a way that it presses against the side faces of the rod-shaped plugelement and thereby brings about a high degree of friction between thespring element and the rod-shaped plug element.

In a preferred embodiment, the energy absorbing device has a skirt whichreaches around the circumference of the feeder body and has in adirection perpendicular to the bottom side of the plate-shaped elementan extent which corresponds at least to the length of the rod-shapedplug elements. In this way, grains of molding material are preventedfrom penetrating into a spacing between the top side of the feeder bodyand the bottom side of the energy absorbing device during theintroduction of the molding material and falling from there for exampleinto the feeder cavity.

According to a further preferred embodiment, a constriction is providedon or near the bottom side of the feeder body to form a breaking edge.Since the feeder insert according to the invention can be placeddirectly on the pattern plate, the position of the constriction inrelation to the surface of the casting is defined, so that a breakingedge for the knocking off of the residual feeder can be arranged at aspecific position. As a result, the effort required for cleaning thesurface of the casting after the residual feeder has been knocked off issignificantly reduced.

The invention is explained in more detail below with reference to anaccompanying drawing. The same items are provided with the samedesignations. In the figures specifically:

FIG. 1 shows a cross section through a feeder insert according to theinvention before compaction;

FIG. 2 shows a cross section through the feeder insert represented inFIG. 1 after compaction;

FIG. 3 shows a longitudinal section through a further embodiment of thefeeder insert according to the invention before compaction;

FIG. 4 shows a longitudinal section and a cross section through a sleeveintroduced into the top side of the feeder body; and

FIG. 5 shows a longitudinal section through a second embodiment of asleeve introduced into the top side of the feeder body.

FIG. 1 shows a longitudinal section through a first embodiment of theshield feeder or plug feeder according to the invention along alongitudinal axis 13 of the feeder. The feeder insert comprises a feederbody 1, which encloses a feeder cavity 2. Provided toward the bottomside of the feeder body is an insert 3, by which a constriction can beformed to form a breaking edge. The insert 3 consists for example ofsteel sheet, wood or similar material. The feeder cavity 2 ends in anoutlet opening 4, via which the feeder cavity 2 is in connection withthe cavity of the casting mold. For the production of the casting mold,a pattern plate 5 takes the place of the cavity of the casting mold. Ledthrough the outlet opening 4 is a mandrel 6, which is fastened on thepattern plate 5 and by which the feeder body 1 is fixed in its position.On the top side 7 of the feeder body 1, two depressions 8 in the form ofa sleeve are introduced into the feeder body 1. The sleeve may beproduced from metal, wood, plastic or similar materials and be insertedin corresponding depressions in the feeder body 1. However, the sleevemay also be formed directly in the material of the feeder body. Insertedrespectively in the depressions 8 are rod-shaped plugs 9, which carry aplate-shaped element 10. The diameter of the plugs correspondsapproximately to the diameter of the depressions 8. Devices whichprevent the rod-shaped plugs 9 from penetrating completely into thedepressions 8 are provided in the depressions 8. As a result, theplate-shaped element 10 is kept at a specific distance from the top side7 of the feeder body 1. Provided along the outer circumference of theplate-shaped element 10 is a skirt 11, which is chosen to be of such asize that no molding material can penetrate into the intermediate spacebetween the plate-shaped element 10 and the top side 7 of the feederbody 1 during the introduction of molding material. As a result, theplate-shaped element 10 comprises a shield- or boss-like form. Theplate-shaped element 10 and the skirt 11 consist for example of steelsheet, wood, plastic or similar materials. Since the feeder insert isfixed on the pattern plate 5, molding material 12 is arranged around thefeeder insert and compacted. The forces acting during the compactionhave the effect that the plate-shaped element 10 is displaced in thedirection of the longitudinal axis 13 of the feeder toward the top side7 of the feeder body 1. As a result, the rod-shaped plugs 9 penetrateinto the depressions 8. Interactions between the rod-shaped plug 9 andthe sleeve 8 have the effect that energy is destroyed, for example byfriction or deformation, and so prevent the feeder body 1 from beingcompressed. In the case of the embodiment represented in FIG. 2, aftercompaction the plate-shaped element 10 rests on the top side 7 of thefeeder body 1. The feeder insert is surrounded on all sides by compactedmolding material 12. Subsequently, the mandrel 6 and the pattern plate 5are also removed, so that the casting mold is obtained. Arranged at thetransition between the feeder cavity 2 and the cavity of the castingmold is a constriction 14, which after casting serves as a breaking edgefor knocking off a residual part of the feeder.

In FIG. 3, a further embodiment of the feeder insert according to theinvention is represented in longitudinal section. In the case of thisembodiment, apart from the outlet opening 4 arranged on the bottom side,the feeder body 1 has an opening 15 in the top side of the feeder body1. The embodiment represented in FIG. 3 is therefore formed as an openshield feeder or plug feeder. As in the case of the embodimentrepresented in FIGS. 1 and 2, depressions 8 are introduced into the topside 7 of the feeder body 1. The rod-shaped plugs 9 of the plate-shapedelement 10 are inserted in these depressions. Molding material is thenintroduced around the feeder insert, as explained with respect to FIGS.1 and 2, and this material is subsequently compacted. In this case, theplate-shaped element 10 is moved in the direction of the longitudinalaxis 13 of the feeder toward the top side 7 of the feeder body 1. Byinteraction between the rod-shaped plug 9 and the depression 8, theforce acting on the feeder body 1 in the direction of the longitudinalaxis 13 of the feeder during the compaction of the molding material isabsorbed and the energy is consumed, so that no compression of thefeeder body 1 takes place and significantly higher forces can be usedfor the compression molding.

FIG. 4 shows a preferred embodiment of the depressions 8. Starting fromthe top side 7 of the feeder body, a depression 8 is introduced into thefeeder body 1. FIG. 4 b shows a longitudinal section through thedepression 8 along a longitudinal axis 16. Arranged along the wall ofthe depression 8 are ridges 17, by which the cross section of thedepression 8 is constricted. The ridges 17 run parallel to thelongitudinal axis 16, the thickness of the ridges, i.e. their extentinto the interior space of the depression 8, increasing as they becomeincreasingly further away from the surface 7. In FIG. 4 a, a crosssection along the line a-a, shown in FIG. 4 b, is represented.

It can be seen that a number of ridges 17 are arranged on the outer wallof the depression 8, whereby the cross section of the depression 8 isconstricted. If a rod-shaped plug 9 (not shown) is then inserted intothe depression 8, it can initially be pushed into the depression 8 onlyto a certain depth. When pushed in further, a frictional force isproduced between the ridges 17 and the wall of the rod-shaped plug 9. Inthis case, the ridges 17 may also be deformed. When this happens, energyis consumed, so that the force exerted on the plate-shaped element bythe compaction of the molding material is absorbed and the energyintroduced can be destroyed. The embodiment of the depression 8represented in FIG. 4 can be obtained by the appropriate structure beingformed directly in the material of the feeder body 1. However, it isalso possible to produce an appropriate sleeve, which is then insertedinto a corresponding depression in the feeder body 1.

In FIG. 5, a further embodiment of the depression 8 is represented as alongitudinal section. Inserted in the depression 8 is a sleeve 18, thewall of which runs along the wall of the depression 8. The sleeve 18 mayalso have a collar 19, which rests on the top side 7 of the feeder body1. Spring elements are arranged in the sleeve 18. These may beconstructed for example from spring steel or plastic. The springelements 20 can be moved with their one end in the direction of the wallof the sleeve 18, which is represented by the arrow 21. If a rod-shapedplug element 9 (not shown) is then inserted into the interior space ofthe sleeve 18, it initially comes to bear against the spring elements20. If pressure is then exerted on the rod-shaped plug elements 9 in thedirection of the longitudinal axis 16, the spring elements 20 arepivoted at their lower termination in the direction of the wall of thesleeve 18. They thereby oppose the movement of the rod-shaped plugelements with a counterforce, whereby the force exerted on theplate-shaped element 10 (not shown) is absorbed and the energyintroduced is destroyed. The sleeve 18 may be produced from any suitablematerial. Suitable materials are, for example, steel or plastic.

1. A feeder insert for inserting into a casting mold used for castingmetals, comprising a feeder body, which extends along a longitudinalaxis of the feeder insert and comprises a feeder cavity, a bottom sidein communication with the casting mold, and a top side that is situatedopposite the bottom side, and an energy absorbing device provided on thetop side of the feeder body.
 2. The feeder insert as claimed in claim 1,characterized in that the energy absorbing device covers at least thetop side of the feeder body.
 3. The feeder insert as claimed in claim 1,characterized in that the energy absorbing device comprises adeformation element.
 4. The feeder insert as claimed in claim 1,characterized in that the energy absorbing device comprises an elasticelement.
 5. The feeder insert as claimed in claim 1, characterized inthat the energy absorbing device comprises a friction element.
 6. Thefeeder insert as claimed in claim 1, characterized in that the energyabsorbing device comprises a plate-shaped element which is arrangedgenerally perpendicular to the longitudinal axis of the feeder insert.7. The feeder insert as claimed in claim 6, characterized in that theplate-shaped element has at least one continuation element and thefeeder body has at least one depression extending inward from the topside of the feeder body into which the continuation element is received.8. The feeder insert as claimed in claim 7, characterized in that thecontinuation element comprises a rod-shaped plug element and thedepression comprises a sleeve.
 9. The feeder insert as claimed in claim8, wherein ridges are that arranged along a wall of the sleeve such thattheir diameter within the sleeve decreases as they extend into thefeeder body from the topside of the feeder body.
 10. The feeder insertas claimed in claim 8, wherein the sleeve further comprises a springelement which produces a counterforce when the rod-shaped plug elementis inserted into the sleeve.
 11. The feeder insert as claimed in claim1, characterized in that the energy absorbing device further comprises askirt (11) which reaches around the upper circumference of the feederbody.
 12. The feeder insert as claimed in claim 1, wherein the feederbody further comprises a constriction on or near the bottom side of thefeeder body to form a breaking edge.
 13. The feeder insert of claim 6wherein the plate shaped element extends outward at least to a maximumcross section of the feeder body.
 14. The feeder insert of claim 9wherein a diameter of the plug element is smaller than the diameter ofthe sleeve.
 15. A feeder insert for inserting into a casting mold usedfor casting metal comprising a feeder body which comprises a feedercavity, a bottom side, a top side and an energy absorbing deviceintroduced into one or more sleeves in the top side of the feeder body.16. The feeder insert as claimed in claim 15, characterized in that theenergy absorbing device comprises a deformation element.
 17. The feederinsert as claimed in claim 15 characterized in that the energy absorbingdevice comprises an elastic element.
 18. The feeder insert as claimed inclaim 15, characterized in that the energy absorbing device comprises afriction element.
 19. The feeder insert as claimed in claim 15, whereinthe sleeve further comprises a spring element which produces acounterforce when the energy absorbing device is inserted into thesleeve.
 20. The feeder insert as claimed in claim 15, wherein the feederbody further comprises a constriction on or near the bottom side of thefeeder body which forms a breaking edge.